Alternanthera

Annual or perennial herbs, sometimes becoming woody at base, prostrate or erect to floating or scrambling. Leaves opposite, entire. Inflorescences heads or short spikes, axillary, sessile or pedunculate, solitary or fasciculate, bracteate; bracts persistent. Flowers bisexual, solitary in axils of bracts; bracteoles 2, usually shorter than perianth, persistent or not; perianth falling with fruit. Tepals 4 or 5, free or concrescent at base, similar to very dissimilar, glabrous or furnished with smooth or denticulate hairs. Stamens 2-5, some occasionally anantherous, hypogynous; filaments monadelphous at base into a cup or tube, alternating with large and laciniate to small pseudostaminodes or these rarely obsolete; anthers 1-thecous. Ovary suborbicular or obovate in outline, usually compressed; ovule solitary, pendulous, basal; style short or absent; stigma capitellate. Capsule thin-walled or sometimes corky, indehiscent. Seeds +/- lenticular. x= 17 (7, 8, 9, 10) (high polyploidy) .